1. Field of the Invention
The present invention relates to method and apparatus for developing, fixing, and processing silver salt photosensitive material including printing paper and photosensitive paper and films for direct plate making.
2. Description of the Prior Art
process cameras are applicable to produce a plate directly from an original for in-plant printing, as offset print and mimeographing. A photosensitive material used for such reproduction generally consists of plural layers of different functions adhering to a water proof base sheet. The laminate includes: a layer for preventing halation; a layer of photosensitive silver salt emulsion; and a hydrophilic layer mainly composed of gelatin with nuclei for physical development such as silver dispersed therein. Irradiation with light changes properties of the emulsion layer. In portions irradiated with light, diffusion of reduced silver from the emulsion layer to the surface layer under the influence of developer is efficiently prevented. On the contrary, in other portions without irradiation, silver halide is complexed and diffused from the emulsion layer to the surface layer. The silver halide diffused onto the surface is physically developed to deposit metallic silver. In subsequent fixation, printing ink is mounted only on lipophilic portions with deposited metallic silver and is not on other portions. A plate for in-plant printing is accordingly prepared.
The photosensitive material reacts with processing solution such as developer at a high rate. A momentary hold of the material in the processing solution or rough surface of the solution may cause unevenness of development or other processes. Still processing solution is hence required to maintain high processing quality. A method proposed to fulfill the requirement is that photosensitive material is soaked in a large volume of processing solution such as developer or fixer stored in a tank. In this case, there is need of large apparatus or equipment for storing a large volume of processing solution.
A photosensitive material soaked in a large volume of processing solution is conveyed slowly so as to keep the surface still, and is taken out of the process tank on completion of processing such as development or fixation. Processing solution in which the photosensitive material is drenched, is efficiently removed with a pair of wring rollers disposed opposite to each other in the down stream of the process tank, so that contamination with the processing solution is prevented. The pair of wring rollers also composes part of a transport system for taking the photosensitive material out of the process tank and transferring the material to subsequent steps.
This method, however, has some drawbacks: a large volume of processing solution stored in the process tank deteriorates with a number of photosensitive materials processed, and alkaline developer in the tank is oxidized with the elapse of time. The changeable properties makes the quality of processing unstable. Frequent replacement of processing solution each after completion of processing of a predetermined number of photosensitive materials is essential to maintain the processing or developing quality. The replacement is, however, time consuming and furthermore changes the processing performance drastically.
This conventional method further requires a relatively long warm-up time for raising the temperature of processing solution to an optimal value. A large capacity of temperature control heater is needed to shorten the warm-up time. It is also difficult to maintain the constant temperature of processing solution in the large volume of tank.
On the other hand, a smaller process tank and thereby a smaller volume of processing solution resuscitate the problem of uneven development or processing. Furthermore, slow transport of photosensitive material through the process tank is required to complete the processing; namely, processing in the smaller tank is time consuming. In winter or cold districts, cold photosensitive material lowers the temperature of processing solution drastically and causes unstable or poor quality of processing.
A further problem of the convention method is sludge accumulating on the bottom of the process tank through development and developer wring processes. Sludge is formed by elution of gelatin from the surface layer of the photosensitive material and by shavings generated when a roll of photosensitive material is cut to a predetermined size. Sludge accumulates on and adheres to the bottom of the tank and is not readily flown away on draining of processing solution; hence additional washing of the tank is required to remove the sludge. Sludge accumulated on the bottom prevents smooth conveyance of the photosensitive material and causes a momentary hold of the photosensitive material in processing solution or rough surface of the solution, resulting in uneven development.
Used developer wrung by the wring rollers returns to the process tank and accelerates deterioration of developer in the tank. Furthermore, sludge in the developer adheres to and accumulates on the surface of the wring rollers to cause difference in level, thus preventing sufficient engagement between the rollers.
Used processing solution wrung by the opposite rollers is collected in the vicinity of the inlet of the photosensitive material and flows along the surface of the photosensitive material. The used processing solution returning to the process tank accelerates deterioration of the developer, thus lowering the quality of development. Furthermore, the used developer on the surface of the photosensitive material causes developing unevenness and poor quality of processed material.